Investigators analyzed data from 356 elderly people (average age 78) in Pittsburgh who were followed for more than 15 years. They found that stiff arteries were a good predictor of dementia.

Specifically, those seniors with higher levels of arterial stiffness were 60 percent more likely to develop dementia than those with lower levels, though the study did not prove that stiffer arteries caused dementia.

Even minor signs of brain disease weren't as good a predictor of dementia as arterial stiffness, according to the researchers.

"As the large arteries get stiffer, their ability to cushion the pumping of blood from the heart is diminished, and that transmits increased pulsing force to the brain, which contributes to silent brain damage that increases dementia risk," explained senior study author Rachel Mackey. She's an assistant professor of epidemiology at the University of Pittsburgh.

"Although arterial stiffness is associated with markers of silent, or subclinical, brain damage and cognitive decline, until now, it was not clear that arterial stiffness was associated with the risk of dementia," Mackey said in a university news release.

The good news is that arterial stiffness can be reduced by taking drugs to treat high blood pressure and by making lifestyle changes, the researchers said.

For example, the study found that exercise at an average age of 73 was associated with lower arterial stiffness five years later.

"What's exciting to think about is that the strong association of arterial stiffness to dementia in old age suggests that even at age 70 or 80, we might still be able to delay or prevent the onset of dementia," Mackey said.

The study was published Oct. 16 in the Journal of Alzheimer's Disease.